Seasonal Abundance Distribution and Catch Per Unit Effort of Fishes in the Swartkops Estuary

Catch per unit effort was obtained for the nekton of the Swartkops estuary near Port Elizabeth by means of gill netting. Fifty gill net catches were made in which 1 269 fish were caught in areas representative of the mouth, middle and upper reaches of the estuary. Pomadasys commersonni, already shown to be the most abundant angling species in the estuary, dominated gill net catches both in terms of mass (29%) and numbers (17%). The family Mugilidae (five species) comprised 25% of the mass and 42% of the numbers caught. Environmental factors and availability of food that might determine distribution offish in the estuary are discussed. The largest mean mass per individual was found in Chanos chanos (4 473 g), Elops machnata (1 656 g) and Valamugil buchanani (1 580 g). Lowest mean masses were recorded for Monodactylus falciformis (63 g), Rhabdosargus holubi (88 g) and Liza dumerili (94 g).     

The fish community of the berg river estuary and an assessment of the likely effects of reduced freshwater inflows

Data concerning the species composition, abundance and distribution of fishes inhabiting the Berg River estuary are presented and used to assess the value of the estuary to fish, and the likely eflects of reduced freshwater inflows. A total of 31 species was recorded, eight of which were classified as estuarine residents, 11 as marine estuarine-opportunists, six as marine stragglers and six were freshwater species. Liza richard- sonii, an opportunist, was the most abundant (54% N) and widely distributed species encountered during the winter and summer seine-net surveys. Three other species (all residents) contributed more than 10% of the total catch; Atherina breviceps and Caffrogobius nudiceps occurring most abundantly in the lower estuary, and Gilchristella aestuaria in the middle estuary. The low number of species compared with estuaries in other regions of the South African coast reflect a well-established marine biogeographical trend. The higher proportions ol resident species, entirely dependent species and partially dependent species suggest, however, that west coast estuaries may be more important to the fish that inhabit them than are estuaries in other regions. It is concluded that the fish community of the estuary is already suffering the effects of habitat degradation and that further reductions in freshwater inllows are not desirable.     

Ecology of southern African estuaries: Part XIII. The Palmiet River estuary in the south-western Cape

The Palmiet estuary is only 1,67 km in length, but has a relatively large catchment of 539 km². Rain falls largely during winter when it scours the estuary and widens the mouth, but by late summer the mouth narrows and, in some years, may close. The estuary never closes for more than a few months, and salinities are normal. The entire estuary has clear bottom water and high bottom salinities, but the surface waters are usually fresh and darkly stained with humic acid. This permanent stratification allows many marine species to penetrate the estuary.

Owing to the scouring in winter, the sediments are coarse, >98% consisting of sand and gravel, with a low organic content. In situ primary production is low, contributing only about one fifth of the organic material in the system, the rest being imported from the river and the sea. Species richness is low, only 28 species of invertebrates being recorded, but many of these occur in enormous numbers. Callianassa kraussi plays a crucial role, trapping fine particles around its burrows and locally enhancing the organic content of the sediments. Its faeces are an important vehicle for the concentration and turnover of organic matter.

Four of the 19 species of fish recorded breed in the estuary, the rest being represented largely by juveniles or small adults. Only three species occurred in the estuary year-round, the other species being absent during the period that the estuary is in flood.

Floods and a relatively high flow of river water are critical to keeping the estuary open. If, as proposed, a dam is built on the river, steps will have to be taken to ensure that the mouth is kept open. A related problem will be the reduction of organic material entering the estuary from the river and the sea.     

Euryhaline zooplankton of the Sundays estuary and notes on trophic relationships

The euryhaline component of the Zooplankton in the Sundays River estuary was sampled monthly at 10 stations from August 1979 to April 1981. In deeper regions surface and near-bottom samples were taken (Stations 1-7) using WP2 nets. Shallow (< 2,0 m) stations were sampled in surface waters only. Water temperature ranged between 14-27 °C. A full salinity gradient was present and salinity stratification was well developed. Acartia longipatella was most abundant during winter and spring (maximum 73 300 m^-3) in the lower estuary. The interaction of temperature and salinity as factors regulating temporal and spatial distribution was evident, these factors also interacting in the water column owing to stratification. The pioneer copepod species, seudodiaptomus hessei, attained high abundance following floods or increased river inflow. Three species of mysid shrimps were common in the plankton in summer, each species showing clear zones of maximum distribution. Zooplankton standing stock (dry mass) ranged from < 10 mg m^-3 to 1 450 mg m^-3 In surface samples and < 10 mg m ^-3 to 8 275 mg m ^-3 in bottom samples. Contribution of mysids to standing stock was rarely less than 70% and often exceeded 90%. Differences in standing stock between surface and bottom samples were owing to behavioural differences between the Zooplankton species, particularly the mysids. Behavioural adaptations play an important role in the retention of the indigenous Zooplankton in the estuary. Aspects of trophic relationships are discussed and demonstrate the significance of the Zooplankton in the transfer of energy to higher trophic levels In this estuary.     

Mysidacea of the Mtentu River Estuary,Transkei, South Africa

The Mtentu River has a straight open tidal estuary flowing between steep grassy or indigenous forest-covered slopes. Total high-water surface area is about 0,3 km.^a The zooplankton was studied by periodic sampling over a period of thirteen months. Some physical characteristics of the estuary are presented. The seasonal and spacial distribution and relative importance of four species of mysid, is discussed. The most common mysid in the estuary was Mesopodopsis africana, although Rhopalophthalmus terrcmatalis, in view of its larger size, contributed more to the overall mass of mysids in the samples.     

Factors Influencing the Recruitment of Juvenile Fishes into the Mhlanga Estuary

The migration of juvenile fishes (<5 cm) into the temporarily open Mhlanga estuary was monitored to determine the effects of different opening periods on immigration. The estuary opened at the end of January 1978 following a nine month closed phase. Only two marine species were recorded entering the estuary in February, compared to 11 species in November 1978. The estuary was closed between April and September. The large November recruitment may be attributed to the abundance of juvenile fishes in the sea adjacent to the estuary, whereas by February very few juveniles were present in Natal inshore waters. Estuarine and freshwater fish species were found to breed inside the estuary during the closed phase when environmental conditions were relatively stable. Mechanisms employed by these species to prevent eggs and larvae from being swept out to sea are discussed, as are strategies used by marine species to ensure recruitment during the very short open phase of the estuary.     

Shallow-Water Trawling Off the Swartkops Estuary,Algoa Bay

Juvenile fish occurring in Algoa Bay off the mouth of the Swartkops estuary were collected using a 3-m beam trawl. Pomadasys ollvaceum, Engraulis capensis, Caffrogoblus agulhensls, Argyrosomus hololepidotus and Galeichthys feliceps were the most abundant species in the trawl catches. Despite the proximity of the Swartkops estuary the trawls failed to capture species which are abundant as Juveniles in the estuary and it is concluded that the estuary has little influence on the juvenile fish fauna outside the mouth.     

我国补血草属野生植物资源的分布及研究现状

补血草属植物具有很高的开发利用价值,但目前尚处于基础研究阶段,对其资源的利用和开发还没有形成产业化。文章概述了我国补血草属植物资源的分布及近年来的研究现状,旨在为补血草属植物的开发利用和产业化发展提供科学依据。     

Abundance,Distribution and Species Composition of Fish Larvae in the Swartkops Estuary

A two-year quantitative survey of the ichthyoplankton of the Swartkops estuary has resulted in the identification of 17 larval fish. The ichthyoplankton was present through all months of the year, but was only abundant during the summer months (November-February). During both years sampled, thehighest densities were recorded in December. An attemptwas made to correlate the data with environmental parameters such as temperature, salinity and rainfall. The ichthyoplankton of the Swartkops is dominated by few species. The family Gobiidae (59,44%) and a clupeid species, Gilchristella aestuarius (31,12%), accounted for 90,56% of all the fish larvae sampled. The family Gobiidae were most common in the mouth and lower reaches of the estuary, while G. aestuarius dominated the mid- and upper estuary.     

鸭茅物种的起源、分布及其遗传多样性研究进展

鸭茅（Dactylis glomerata）是世界著名的优良牧草之一,在世界范围内分布广泛、栽培历史悠久。自然界野生鸭茅种质资源丰富、基因资源优良、开发利用潜力大,是鸭茅育种和品种改良的重要基础。了解该物种的分布和起源,对于资源的收集、保护和利用及开展相关基础研究具有重要意义。本文对鸭茅的分类、起源及遗传多样性研究进展进行综述,并对鸭茅种质资源研究中存在的问题提出了建议,以期更好的研究和利用这一优良的牧草资源。     

福建省5种鸟类新纪录种和亚种

2003年7月18日在平潭岛观测到白玄鸥7只；2004年1月18日在闽江河口观测到白领翡翠1只；2004年11月27日在闽江河口观测到白眼潜鸭30只；2006年5月3日在福建龙栖山国家级自然保护区内观测到斑头大翠鸟2只，上述4种均为福建省鸟类新纪录。2003-2005年冬季在闽江河口和兴化湾均观测到黄腿银鸥，这一亚种为福建省新纪录。     

A survey of the fish fauna of Transkei estuaries Part Two: The Mbashe Estuary

The species composition, seasonal abundance and spatial distribution of the fish fauna of the Mbashe estuary (8 km long) was determined by means of gill nets. During the 37 month survey period, 2908 fish (2319,8 kg), comprising 27 species, were caught. The family Mugilidae, representing 58,8% of the numbers and 57,4% of the biomass, predominated the catches. In terms of biomass M. cephalus, A. hololepidotus and P. commersonnii were the most important species. Seasonal patterns for 10 of the 27 species were observed. M. cephalus, A. hololepidotus and L. amia were more abundant in spring/summer, E machnata and V. buchanani in spring, P. commersonnii and L. tricuspidens increased numerically in winter and M. capensis in autumn, Johnius dussumieri and Valamugil cunnesius were rare in winter and summer, respectively. Largest catches were made in the middle reaches of the estuary followed by the upper and lower reaches, respectively.     

Experimental Control of Metacercariae of the Yellow Grub Clinostomum marginatum in Channel Catfish

Abstract

Metacercariae of yellow grub Clinostomum marginatum in the flesh of farm-raised channel catfish Ictalurus punctatus pose a potential marketing problem to fish farmers. Infected fish may not be marketable. Three compounds were tested as possible control agents. Droncit (praziquantel) and Masoten (trichlorfon) were used separately as a bath treatment. Droncit and ivermectin were injected into the musculature to control yellow grub metacercariae. The two treatment rates were 0.65 mg/L plus 15 mg/kg offish as a bath treatment and 25 mg/kg offish as an injected treatment for Droncit. Masoten was treated at a rate of 2 mg/L as a bath treatment and ivermectin (1% solution) was injected at a rate of 0.022 mL/kg. Droncit significantly reduced metacercariae in both bath and injection treatments. Ivermectin also significantly reduced the number of metacercariae, but was not as effective as Droncit. Masoten was ineffective. More study is needed to obtain dosage rates for Droncit and ivermectin that would eliminate yellow grub metacercariae from the flesh of channel catfish.     

Ecology of southern African estuaries Part XI. Mngazana: a mangrove estuary in Transkei

Mngazana is a rich estuary dominated by mangroves and containing a diversity of both invertebrates and fish. Its richness is mainly due to favourable physical conditions. The invertebrate fauna includes temperate, tropical, and subtropical species, predominating in the lower reaches, middle reaches and head respectively. The fish have affinities with the tropics in summer, while in winter many warm-temperate species increase in numbers. In comparison with the fauna of soft substrates, that of rocks has a higher percentage of stenohaline and estuarine forms, and a more restricted distribution. The rocky habitat in estuaries favours greater specialization with respect to salinity tolerance. A high percentage of the biomass of invertebrates in soft substrates consists of detritivores, and the biomass is related to the organic content of the substrate. Mangrove mud has the hlghest organic content and supports the highest biomass, but few species can tolerate the conditions there. Mangroves are probably the major primary producers in the system.     

Aspects on The Ecology of Labeo Capensis and Labeo Umbratus in The Vaal River

Studies on bivalves in the Swartkops estuary have indicated that spatfall occurs during late summer. After adult populations had been dtc'nvttfrrt by floods in 1971 spat made up a large proportion of the bivalve population in 1973. Growth rates vary at different intertidal levels and in different parts of the estuary and growth has been shown to vary seasonally. In two species age determinations from growth rings corresponded well with age determinations from size frequency histograms.     

不同类型高寒草地群落物种特征和均匀度的重要性

通过对不同类型草地生产力与物种特征(重要值)、均匀度之间的关系研究,结果表明:群落物种特征(重要值)与生产力之间呈极显著的线性关系;物种均匀度与生产力之间呈负线性关系,但差异不显著.在自然生态系统中,由于物种间的相互作用(资源的竞争利用),物种数目在不同类型草地群落的物种组成上的不均匀分布,导致不同生境条件下均匀度的异同.     

The Zooplankton of Mgazana,A Mangrove Estuary in Transkei,Southern Africa

Mgazana, a mangrove estuary inTranskei, was investigated from May 1972 to March 1973 at six-week intervals. Salinities were consistently above 25 parts per thousand in the middle and lower estuary. In the upper estuary the salinity varied between 4 and 29 parts per thousand. Water temperatures varied between I5,5°C and 28°C. One hundred and fifteen taxa of zooplankton organisms were recorded in the samples. The copepods Acartia naialensis and Oithona brevicornis reached high population densities and numbers exceeding 100 000/m³ of water were recorded. Mysids were major contributors to zooplankton biomass. A maximum biomass of I 200 mg/m³ was recorded in February in the middle estuary and was attributed to the mysid Mesopodopsis africana. Species of mysids showed clear seasonal and spatial patterns of distribution in the estuary.     

Foraging technique and prey‐handling time in black‐necked stork (Ephippiorhynchus asiaticus)

The foraging technique and prey‐handling time of the black‐necked stork (Ephippiorhynchus asiaticus) was studied in Dudhwa National Park, India, from January 1996 to June 1997. The habitat in which the storks foraged played an important role in selecting a particular technique to procure food. Black‐necked storks mostly foraged using a tactile technique (>90%), but sometimes foraged visually. When the water level was estimated to be less than 60 cm, the storks foraged using tactile techniques. There was no difference in the feeding techniques of male and female storks. Foraging attempt rates varied between the sexes in summer (May) and during late winter (February) in 1997. The search time for prey increased when the water level was high and fish were widely distributed. Decreases in water level resulted in concentration offish in certain areas and this contributed to high fish‐catching rates by black‐necked storks. Males had a higher success rate offish capture than females. However, females captured longer fish than males. Prey‐handling time increased in both sexes as fish length increased. Fish 4–6 cm long were most frequently taken by the foraging storks.     

甘肃省麻黄属野生种质资源及保护利用

目的：调查甘肃省麻黄属植物野生种质资源现状,并提出保护利用建议,为麻黄属植物的资源保护和可持续利用提供依据。方法：在查阅文献和标本馆标本记录的基础上,采用重点区域实地调查和走访调查相结合的方法,对甘肃省麻黄属植物的种质资源进行整理分析,就麻黄属植物的资源现状和分布格局进行研究。结果：查实甘肃产麻黄属植物7种,订正了文献中常出现的异名,并绘制了甘肃省麻黄属植物分布图;市售本地麻黄多为中麻黄,偶见收购膜果麻黄,民间使用各种均有。结论：应进一步加大法律法规的宣传执行力度,规范野生麻黄采收方法,积极开展社区生物多样性保护工作,加强种质收集和筛选,做好麻黄种植的技术支持和市场引导。     

海南省禾本科饲用植物资源及其营养评价

全面考察海南省及其周边岛屿的禾本科饲用植物资源及其分布情况,其中海南省可供饲用的禾本科饲用植物104属270种,并对49个种的234份材料进行化学成分分析。